The present invention relates to a device for determining the wheel and/or axle geometry of motor vehicles in an inspection room using an optical measuring device having at least one optical image pick-up device from at least two different perspectives, having a marking device, which includes a measuring feature arrangement existing or arranged on the wheel, and having an evaluation unit.
A device of this kind is described in the German Patent No. DE 42 12 426 C 1. In the case of this known device, to determine a vehicle""s wheel track and camber, characteristic regions of the wheels are recorded by video cameras. The wheel in question is provided outside of its axle with a marking that is able to be registered optically. The marking is recorded during rotation of the wheel by two synchronized video cameras. The relative positions of the corresponding axles are determined from the spatial positions of the markings on the wheels. The video cameras are arranged symmetrically to the axle of the corresponding wheel, the vehicle resting on rollers, and the wheels turning in roller prisms. When this system is used, the possibilities for measuring wheel or axle geometries are limited to wheel track and camber measurements, and substantial outlay is required to adjust the axle geometry. It is not possible to correct the axle geometry on the roller test stand.
The object of the present invention is to make available a device of the type mentioned at the outset, which, while providing a simplified operation, will enable one to obtain more information with respect to wheel or axle geometry, and which will permit corrections to be made on the chassis during the measuring operation (for example, above an inspection pit). There is no need for adjustment of the image pick-up device.
The present invention provides that the marking device has a reference feature arrangement including at least three reference features per image recording position, the position of the reference features in the inspection room being known in the evaluation device, and that the measuring feature arrangement includes at least three measuring features per wheel.
Using this device, the driving axis and, in addition, geometrical wheel and axle data named in the following can be automatically determined arithmetically in the evaluation device, using known algorithms: individual track for each wheel, total track for each wheel pair, camber for each wheel, front/back wheel offset, right/left lateral offset, track width difference, axle offset, steering angle, caster, steering axis inclination, and toe-out on turns, as well as the position of the multi-link independent suspension as a function of the steering angle of each steered wheel, it being extremely simple to position the image pick-up device, due to the integration of the reference features. With the aid of the reference features known in the evaluation device, one can initially determine the camera position and, simultaneously or subsequently, the position of the measuring features relative to the reference features, and from this, one can then derive the mentioned geometrical wheel and axle values.
A simple design, including reference features that are able to be reliably detected, is achieved in that the reference feature configuration has a mount support unit, on which the reference features are provided in the form of reference structures or specially applied reference marks. This enhances the reliability of the measuring results.
If the reference features are not only arranged in an even, planar configuration, but also spatially offset with respect to the image pick-up device, then the evaluation is simplified, as compared to an even configuration of the reference features, while ensuring substantial reliability of the measuring results.
To reliably detect the markings, further benefit is derived from measures which provide for the reference features and/or the measuring features to be designed as retro-reflecting marks, and the image pick-up device as a camera.
If automobile body structures or additional, specially applied automobile body markings are provided as additional measuring features, which are able to be recorded by at least one image pick-up device and included in the evaluation, then, using the same device, in parallel with the geometrical wheel and axle data, one can detect the deflection or load status for each wheel, and/or the inclination of the automobile body in the longitudinal and transverse direction, and if indicated, consider them in vehicle-specific correction calculations.
A cost-effective design of the device is achieved in that, given a static measuring task, only one image pick-up device is provided, which is able to be positioned sequentially at two different positions to mutually detect, in each case, all wheels of the vehicle, or sequentially at two different positions per vehicle side, to mutually detect, in each case, all wheels of this vehicle side, or sequentially, at two different positions per wheel, and that, using the evaluation device, the sequentially recorded image data are able to be stored and evaluated.
In comparison, a simplified operation is achieved in that one measuring unit is provided with at least two image pick-up devices, which are able to be arranged at only one position to jointly record all wheels of the vehicle, sequentially on both vehicle sides at only one position each to jointly record all wheels per vehicle side, or sequentially at only one position per wheel, and that, using the evaluation device, the sequentially recorded image data are able to be stored and evaluated.
A further simplified operation is achieved in that two measuring units are each provided with at least two image pick-up devices; that the two measuring units are placed on both sides of the vehicle in such a way that they each detect the wheels of one vehicle side; or that the two measuring units are placed on one vehicle side in such a way that each detects one wheel; and that both vehicles sides are sequentially detected; or that the two measuring units are placed in such a way that, in each case, one wheel of one vehicle axle is detected on both vehicles sides, and the vehicle axles are sequentially detected; and that using the evaluation device, the sequentially recorded image data are able to be stored and evaluated and; in addition, in that four measuring units are each provided with at least two image pick-up devices to simultaneously record of four wheels of the vehicle.
The acquisition of the measuring data and the evaluation are enhanced in that one measuring unit includes at least three cameras.
The measure which provides for using at least one light source to illuminate the-measuring features and the reference features further enhances the ability to detect the measuring features and the reference features. Having at least one light source in the vicinity of the lens of the image pick-up device(s) facilitates the detection of retro-reflecting measuring and reference features. If provision is made in this context for the light sources to be infrared light-emitting diodes, then any degradation in the light conditions is avoided for the operator of the device at the measuring site.
The wheel features a plurality of vehicles, or also a plurality of measuring stations can be automatically distinguished in that at least one measuring mark per wheel or per vehicle, and/or at least one reference feature bears a coding that is detectable by the image pick-up device. In this context, by encoding at least one of the applied wheel marks, it is especially possible as well, to clearly assign the magnitude of a form error of one wheel rim to the corresponding wheel mark, and to allow for it during subsequent measurements or evaluations, i.e., to correct it.
By applying such measures, one can, for the most part, do without a precise leveling of a measuring station. The device does not have any absolute relation to a normal direction, rather exclusively relative relations to the reference arrangement of the measuring station. For that reason, the extent to which the measuring station is required to be even or level can be minimized to that which is required by the vehicle.
This specification of the obtained geometrical data is not limited to angular units; the data can also be provided as absolute units of length.
The need is eliminated for adjusting the measuring device at the wheel, as required by many systems in known methods heretofore. The positioning of the optical image pick-up device diagonally across from a wheel/wheels and the reference arrangement can be carried out in a simple, approximate manner, and be controlled very easily, for example, using positioning aids.
The measured value acquisition itself takes place in fractions of a second, a higher level of accuracy and, at the same time, a larger measuring range being given for all measured quantities.
The need is eliminated for an angular positioning encoder required in known methods heretofore on rotating plates to determine the size of the steering angle, since this angle is defined by the measuring system itself.
Using the same device, the geometrical wheel and axle data of commercial vehicles can be determined at another measuring station, which is designed to accommodate the dimensions of commercial vehicles. For this, no other testing technology is needed.